Numerous types of bowl and cover assemblies and means for effecting a closure of the cover on the bowl have been devised. However, the present invention provides a bowl and cover which may be easily fabricated from an expanded foam plastic sheet whereby the skirt of the cover contains a semicircular locking member with an interspersion of undercut grooves for venting purposes. Likewise, the present invention provides a lid configuration whereby a plurality of lids can be stacked without creating a vacuum between adjacent stacked lids and thereby preventing vacuum locking. The elimination of vacuum locking allows the covers to be more easily and quickly handled.
Finally, the present invention fills a need in the packaging art for a lightweight disposable container for hot take-out food, such as Japanese or Chinese food. Heretofore, such containers have often been paper cartons which have little heat retention capabilities and exhibit various undesirable structural features. Foam containers have increased heat retention capabilities over paper cartons, however, heretofore such foam containers, as in U.S. Pat. No. 4,341,324, have generally provided for vacuum sealing when the cover is placed onto the bowl. When hot food is vacuum sealed within the container, the container becomes distorted in shape and such distortion often causes the vacuum seal to break, which in turn causes the cover and bowl to separate. The present invention eliminates the problems of paper containers and cartons, and the problems of vacuum sealed foam containers, and provides a container that is capable of retaining its shape and the seal between the bowl and cover when hot food is placed inside, whereby the freshness and heat of the food contained therein is retained.
The present invention comprises a bowl and cover assembly wherein the bowl includes a bottom, an upper annular rim and upwardly extending side walls rising from the margin of the bottom and terminating in the upper annular rim. An integrally formed annular interlocking lip depends radially outward from the annular rim. The annular interlocking lip comprises an annular top sealing surface and an annular edge sealing surface depending downwardly from the margin of the top sealing surface about the peripheral edge of the annular interlocking lip, and the seal between the cover and the bowl is interrupted at at least one location along its annular edge whereby to provide an opening into said bowl and cover assembly.
In another embodiment, on the inside of the annular skirt of the cover are interspersed undercut grooves for venting purposes, numbering six in this embodiment. Between each set of neighboring undercut grooves is a radially inwardly protruding semicircular interlocking bead which extends almost to the edge of each undercut groove. This bead acts as a locking member when the cover is placed on the bowl because the diameter of the semicircular bead is smaller than the diameter of the lip of the bowl.
In yet another embodiment, between the edge of the semicircular interlocking bead and the edge of an undercut groove is a section of thinned foam that lacks the semicircular interlocking bead. Because such section lacks the additional foam used to form the semicircular interlocking bead, and because no interlocking takes place between the cover and the bowl at that location, the cover is more flexible and such configuration allows for annular spring action making it easier to place one'ss fingers under the annular skirt of the cover and remove the cover from the bowl.
In yet another embodiment, the annular skirt of the cover may include an annular trim lip integrally formed with the cover which defines a radially protruding circumferential member extending from the lower edge of the lower downwardly depending portion of the annular skirt remote from the peripheral flange. The junction between the trim lip and the lower downwardly depending portion defines an inwardly facing stacking heel. The shape and circumferential length of the annular skirt and the domed panel of the lid are then selected so that the stacking heel of the upper cover will rest on the annular skirt shoulder of the lower cover thereby preventing formation of a partial vacuum between the upper and lower covers when they are stacked on top of one another.